Method for solidifying sulphur



April B. A AXELRAD ET AL 2,154,257

METHOD FOR SOL IDIFYING SULPHUR Filed Sept. 28, 1937 2 Sheets-Sheet l lNVENTORf mam BY M April 1939. B. A. AXELRAD ET AL 2,154,257

METHOD FOR SOLIDIFYING SULPHUR Filed Sept. 28, 1937 2 Sheets-Sheet 2 0 1 2 3 4 6 AMmP/mz/J 50.4 Pl/l/A? DiCAi/QS/N fiMB/l/f) EMVNTORS BY QM RNEY5 Mew yam Patented Apr. 11, 1939 PATENT OFFlCE METHOD FOR SOLIDIFYING SULPHUR Bernard A. Axelrad and Dougal A. Brooks, Freeport, T'ex., assignors to Freeport Sulphur Company, Freeport, Tex., a corporation of Delaware Application September 28, 1937, Serial No. 166,229

6 Claims.

This invention relates to a method for solidifying sulphur, and particularly to the solidification of sulphur in bins; such sulphur generally being produced by mining by underground fusion, as for example, in the Frasch process.

The invention has for its object generally the avoidance of certain difliculties heretofore encountered in the practice of solidifying and storing sulphur that has been mined as indicated and is in a molten condition, and the improvement of the quality of the resultant product.

A specific object is to reduce the amount of so-called crater sulphur that has heretofore accompanied the solidifying of the sulphur in 1 large storage blocks by reason of the slow cooling of molten sulphur that forms in pools at the discharge points. I

Another object of the invention is to allow a much larger rate of sulphur to be handled with- .out increasing the areaof the bin; or the same tonnage can be handled in smaller bins effecting certain economies.

Another object of this invention is to reduce the labor and difiiculties of operation of the conventional types of discharges that result from the necessity of changing the point of discharge of the sulphur.

Another object of this invention is to make a sulphur of less friability and lower porosity thereby resulting in a product delivered to the consumer of lower moisture content and with a decreased amount of acid contamination.

Still another object of this invention is the elimination of foreign substances by removing discharges, supports, etc. to points outside the bin.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, all. as exemplified in the following detailed disclosure, and the scope of the invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the followingdetailed description taken in connection with the accompanying drawings, in which:

Fig. 1 is a view, partly in vertical section and partly in elevation, of apparatus adapted to discharge molten sulphur and solidify the same in accordance with the invention;

2 is a plan view of the apparatus shown in Fig. 1 and illustrates the distribution in the storage bin achieved by the invention;

Fig. 3 is a vertical sectional View showing the apparatus of the invention, taken on the line 3-3 in Fig. 2;

Fig. 4 is an enlarged fragmentary sectional View of a nozzle provided in accordance with the invention and disposed in discharge position over a body of sulphur in a storage bin; and

Fig. 5 is an explanatory diagram.

In the mining of sulphur by underground fusion, as in the Frasch process, highly heated or superheated water under pressure is discharged into the sulphur-bearing formations and the melted sulphur resulting is raised to the surface by means of an air lift. Prior to the present invention, it was customary to collect the molten sulphur from a number of sulphur wells, in a common container and when a suflicient amount had accumulated, it was pumped to a bin consisting generally of four enclosing walls that are built up from ground level as the sulphur solidifies. The molten sulphur was then flowed into the enclosure made by the four walls and was solidified in successive layers.

The discharge of molten sulphur into the bin was usually intermittent due to the accumulation in the common container and the number of points of discharge into the bin was usually such with respect to the size of the bin that most of the sulphur will have been solidified in the interval between consecutive discharges at the same point. In this manner, huge blocks of solid sulphur have been formed. Such blocks may be, for example, several hundred feet in length and in width and sixty or more feet in height, and contain several hundred thousand tons of sulphur.

The apparatus heretofore used in effecting the solidification of sulphur, as above described, comprised in general a distributing system through which the molten sulphur was pumped from the common container to risers disposed adjacent a side of the bin receiving the sulphur. These risers were generally connected to discharge onto the surface of the previously solidified sulphur through a plurality of adjustable discharge nozzles. The rate of flow from these nozzles was invariably slow, since it is limited by the rate of pumping from the common container. In consequence, a relatively large number of such discharge nozzles and attendant connections were employed over a given area in the bin. A large number of towers, which might be of either wood orsteel, were thus necessary to support the risers and nozzle connections in operative position. Numerous supports of this character tend to contaminate the sulphur product unless suitable offsetting measures be taken, and interfere somewhat with the subsequent breaking and loading operations, preparatory to shipment. The slow discharge necessarily attendant upon this arrangement results in streams at random of liquid sulphur flowing to the colder parts of the underlying solid sulphur, which streams cut deep channels in the surface of the solid sulphur and also form molten pools.

The procedural steps for operating this apparatus, in consequence, is accompanied by certain difficulties, among which may be mentioned the formation of pools or pockets of molten sulphur which collect beneath each discharge point. Here the sulphur solidifies in the form of large crystals with a greenish cast and are usually referred to as crater sulphur. Although of equal purity, this crater sulphur is considered to be an inferior product by the trade and is at a sales disadvantage.

To reduce the tendency to form crater sulphur, the distributors at each discharge point are, as a rule, designed to turn about a vertical axis, thereby providing a number of discharge points for each distributor. The liquid sulphur upon discharging into the bin invariably forms channels, the extent and direction of which depend on the nature and irregularity of the surface. By reason of the cooling and solidification of the sulphur at the edges of the channel, the flowing sulphur builds up to a depth of several inches before solidifying. During the subsequent cooling, a solid crust or sheath forms on the surface of the molten sulphur which by reason of its excellent heat insulating properties prevents the molten sulphur that is beneath from losing its heat to the atmosphere. It is seen, in consequence, that much of the sulphur thus discharged for storage cools at a very slow rate. When finally solidified, this sulphur is very friable and porous and upon blasting prior to loading and shipping operations, for example, loading into gondola cars or other vehicles of transportation, breaks into fragments with a relatively high percentage of fines. A further result is a high physical dust loss in handling and also the retention of considerable amount of moisture upon exposure to rainfall and humid atmospheric conditions.

Also, the sulphur in the bin prior to blasting is relatively free from acid impurities but upon exposure, subsequent to blasting down from the bin, is found to contain acid in amounts varying from mere traces. to objectionable quantities. It has been established also that there are other influencing factors, for example, temperature, moisture content, and length of storage time.

These factors, however, being equal, the amount of acid formed is proportional to the amount of exposed surface area of the sulphur; that is to the fineness and porosity.

We have ascertained, however, from an extensive research that the rate of cooling of molten sulphur is the dominating factor influencing its physical structure (porosity and friability); the friability being inversely proportional to the rate of cooling. Molten sulphur, as produced in the Frasch process, has a content from 4 to 8 per cent. of amorphous sulphur and the amount present in the solid phase is proportional to the rate of cooling.- While the amorphous content apparently influences the frlability, it is possible that the two are independent factors but both affected by the rate of cooling. Since the latter is definitely true, the amorphous content can be taken as a measure of the friability of sulphur, when produced by the Frasch process for various rates of cooling.

The relation of the rate of cooling to friability may be more readily ascertained by reference to the diagram in Fig. of the drawings. Here, abscissae represent friability, while the ordinates show rates of cooling. It is seen that, due to the poor heat conductivity of solid sulphur, solidification, which starts at the surface, proceeds inwardly very slowly. As a result, the rate of cooling depends on the thickness of the body of sulphur in the liquid phase that is poured onto a surface and left to solidify.

In carrying out the steps of the present invention, solidification of the molten sulphur is accomplished by relatively quickly cooling a plurality of relatively thin superposed layers of molten sulphur, each of which is preferably provided by discharging a relatively large batch of molten sulphur in an interval of time of less than one minute upon a surface, which may be that of a previously cooled body of solidified sulphur, in a manner such that the molten sulphur distributes itself in a relatively thin layer of from A; to & inch thick. Such layers achieve a very marked improvement in the rate of cooling as against the former method where layers of from A; inch to several inches thick obtained.

Referring now to the drawings and particularly to Figs. 1, 2 and 3, a conveying and distributing system for the molten sulphur is shown as comprising a main conduit l0, that may be disposed along the ground as shown and leads from a common gathering container (not shown) to points at the side of the bin B which is to ,be filled with solidified sulphur. From the conduit are led one or more distributing risers II that lead upwardly and are supported by means of towers I2 disposed at the side of the bin. Each riser ll discharges into a suitable tank or receptacle I3 that is supported by the tower at a height that provides a suitable discharge head. From the bottom of the tank is led a discharge conduit I4 of relatively large diameter that extends in a generally horizontal direction to a suitable point over the bin and then has a depending portion to which is attached a nozzle l5 that is turned to discharge in a horizontal direction, as shown more fully in Fig. 4. Molten sulphur is, of course, pumped through the conduits l0 and II into the tanks l3 until the latter are properly filled preparatory to discharge. When a tank I3 holds the desired quantity of molten sulphur, it is discharged automatically through discharge pipe l4 and nozzle l5 onto the surface of the previously solidified sulphur l6. Other means are, of course, available to discharge a large volume of liquid in a small interval of time and the use of tanks is given merely as illustrative of suitable means for achieving the step of quickly discharging a relatively largebatch of molten sulphur in accordance with the invention.

Since the rate of flow of molten sulphur from the discharge nozzle is relatively great, the discharged sulphur, shown at IT, has sufficient velocity to fiow rapidly a long distance. Due to the large quantity of sulphur discharged or dumped at one time a relatively large liquid head is produced in the line of flow. This head also produces cross-flow, i. e., flow at right angles to the main line of flow, of such velocity that the previously mentioned crusts and sheaths are not formed and as a result a thin liquid layer of sulphur is spread over a relatively large area, as shown at I8. This thin layer loses its heat rapidly after bonding itself to the surface of the previously solidified sulphur. The step of quickly discharging or dumping the molten sulphur and its subsequent spreading in a thin layer over a large area is accomplished so rapidly that there is no great loss of heat from the molten sulphur. The greater part of the heat is consequently available to maintainthe perfect fusion of the new layer with the previously deposited layer.

Since a very large area may be covered by the type of distributor here employed, it is possible to place the equipment outside the area to be covered, thereby eliminating the possibility of contamination of the sulphur by supporting structures. By way of illustration, with a tank clumping 20 tons of sulphur at one time a lineal spread of about 250 feet adequately serving an area of approximately 50,000 square feet can be obtained. By varying the size and shape of the discharge nozzles and also of the volume and temperature of the sulphur even greater distances and areas can be covered.

Since certain changes in carrying out the above method and in the construction set forth, which embody the invention, may be made without departing from its scope, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Having described our invention, what we claim as new and desire to secure by Letters Patent is:

1. The process of solidifying molten sulphur in bins which comprises discharging into the bin a relatively large volume of molten sulphur of the order of tons at one time and at such a rate and such a temperature that the discharged sulphur spreads itself in a thin layer of an order of from to 1 5' of an inch over a large area.

2. The process of solidifying molten sulphur in bins which comprises discharging a relatively large volume of molten sulphur of the order of tons at one time and at such a rate and such a temperature that the discharged sulphur spreads itself under its own head in a layer that is of the order of to of an inch in thickness, then cooling and solidifying the same, and thereafter similarly cooling and solidifying another superposed layer of sulphur on the first-named layer by discharging another similar large volume of molten sulphur, whereby a mass of solid sulphur is built up.

3. The process of solidifying crude sulphur in bins, which comprises discharging a relatively large volume of sulphur of the order of tons at one time and at such a rate and such a temperature that the discharged sulphur spreads itself under its own head in a layer that is of the order of A; to of an inch in thickness, then cooling and solidifying the same, and thereafter successively cooling and solidifying in a similar manner additional thin layers of sulphur of the same character over the first, whereby to build up a mass of solid sulphur in the bin to a desired height, providing a resulting uniform product of relatively low porosity and of substantially increased strength and hardness.

4! The process of solidifying molten sulphur in bins in a manner which produces a product of relatively low porosity and reduced contact surface area, which process comprises discharging at intervals into the bin a succession of volumes of molten sulphur whose masses are in the order of tons, each Volume being discharged at such a rate and at such a temperature that the step is completed in a period of time less than a minute, permitting each discharged mass to spread itself under its own head in a layer that is in an order of from to i g of an inch in thickness, and cooling and solidifying the succession of layers in superposed array whereby a sulphur product is formed which maintains a character relatively low in moisture, acidity, and other impure contents.

5. The process of solidifying molten sulphur which comprises accumulating a mass of sulphur in the liquid phase in a volume such that it will spread itself over an area of the order of thousands of square feet, discharging suddenly said accumulated mass upon a surface at such a rate and at such a temperature that it freely spreads itself under its own head and forms a layer that is of an order of from to of an inch in thickness, and cooling said layer while adhering to the surface on which it is discharged in a manner which avoids local freezing of any portion prior to the time of general solidification.

6. The process of solidifying molten sulphur which comprises accumulating successively a series of masses of sulphur in the liquid phase, each in a volume that is adapted to spread itself over an area that is of an order of thousands of square feet, discharging in successive intervals said accumulated masses in a sudden manner one upon the other at such a rate and at such a temperature that each discharged mass spreads itself under its own head and forms a layer that is of an order of from to of an inch in thickness, and cooling and solidifying each of said layers in a manner avoiding local freezing prior to the time of general solidification during the interval of no discharge so that a single solid mass may be built up yielding a reduced amount of fines and having increased strength, density, and hardness.

BERNARD A. AXELRAD. DOUGAL A. BROOKS. 

